1 Technical Field
The present invention relates to stators for rotating electric machines that are used in, for example, motor vehicles as electric motors and electric generators.
2 Description of Related Art
Japanese Patent Application Publication No. JP2006-280121A discloses a stator for a rotating electric machine. The stator includes a stator coil that is comprised of a pair of first and second three-phase coils. Each of the first and second three-phase coils includes a plurality of phase windings that are connected in a predetermined manner to form a plurality of connection portions therebetween. The stator coil is mounted on an annular stator core of the stator so that: the first and second three-phase coils are different in phase from each other by 30° in electrical angle; and the connection portions of the first three-phase coil are circumferentially offset from the connection portions of the second three-phase coil. Consequently, the connection portions of the first three-phase coil do not overlap the connection portions of the second three-phase coil.
Moreover, in the stator disclosed in the above patent document, each of the first and second three-phase coils includes three output lead portions. Further, each of the first and second three-phase coils is arranged on the stator core so that two of the three output lead portions of the three-phase coil are located on one circumferential side of the connection portions of the three-phase coil and the remaining one of the three output lead portions is located on the other circumferential side of the connection portions. With such an arrangement, it is possible to reduce the lengths of bridging wires which bridge (or extend to electrically connect) the phase windings of the three-phase coil and different sections of the phase windings.
However, in the stator disclosed in the above patent document, the bridging wires are arranged so as not to interfere with the connection portions. Consequently, the radial distances of the bridging wires from the center of rotation of the rotating electric machine become non-uniform; thus a radially inner peripheral surface of the stator coil which is defined by the connection portions and the bridging wires becomes not smooth. As a result, when the connection portions and the bridging wires are subjected to the flow of cooling air created by a cooling fan of the rotating electric machine which is disposed radially inside the stator, pressure variation may occur on the radially inside of the connection portions and the bridging wires in the circumferential direction of the stator core, thereby increasing the fan noise generated during rotation of the cooling fan.
Moreover, in forming the connection portions, end portions of the phase windings are stripped of insulating coats covering them and electrically connected to one another. Then, an electrically-insulative resin is applied to cover the connection portions so as to electrically isolate them. However, with the structure of the stator disclosed in the above patent document, the connection portions are directly viewable from the radially inside of the stator. In other words, the connection portions are directly exposed to the flow of cooling air created by the cooling fan. Consequently, foreign matter, such as dust and electrolytic solution (e.g., saltwater) may flow to the connection portions along with the flow of cooling air created by the cooling fan, thereby damaging the connection portions. As a result, the environmental resistance of the rotating electric machine may be lowered.